Hi Alan, are you looking for LPR or LPC? From your link, it seems it is just LPC, capture, not machine auto recognition, correct?
If so, this test is relevant: Low Cost License Plate Capture Shootout
Yes LPC in this case. I have looked at yor shootout a few months back. It doesn't look like any of these would work reliably around the clock.
This is an IP CCTV system, so it would be good to find an IP solution but using converters would be OK as well.
IPVMU Certified | 11/25/15 11:44pm
Has anyone tested a Dahua LPR camera? I'm mainly interested in LPC and would greatly appreciate any reports about how these cameras work for LPC. Thank you!
IPVMU Certified | 11/26/15 11:19am
Dahua IP LPR cameras are the ones of interest to me. Thank you for asking.
I haven't tested the ip LPC cameras yet. Outside of the budget of my most recent project where I used a small hd-cvi dvr in addition to the NVR so I could use the same CMS and mobile app.
its certainly affordable enough to warrant a test trial.
I am not sure how much this helps but so far, this is my understanding/testing :
- the dedicated LPC cameras are normal cameras plus a low pass filter and some adjusting of the shutter/iris . This way , the "normal" light gets filtered out and only the IR gets in, thus the dark image with only the plate reflected back
- i got one of those filters from a Photo shop and with the proper camera - where you can adjust exposure ( easier to find in IP world but i would guess CVI/TVI also ) - it does work like so
- next problem is getting some IR light on the plate to reflect back to the lens. This happens either with a very narrow angle IR light and adjusted angle of the lens+illuminator or with a "special" bullet camera where the LEDs for some reason give a very narrow light. Here obviously the angles need to be as low as possible ( horizontal lines ) so the target would ideally be a bit far a way and you use a longer narrower lens.
So, in my view, these are the main factors :
1 adjust exposure low = dark image so you exclude most text from vans and etc.
2 low pass filter = only IR gets in the camera
3 angle of IR -> Plate -> lens as low as posible so the plate "shines" back ( either a "good bullet" or adjusting the IR and camera bracket )
In the end it is just like shining a mirror into someone's eye ... all about angles. Hope i made myself understood, otherwise ... sorry.
PS On Milestone's website there is a manual for their ANPR software and that has a section about the angles thing and how to improve reading
PS2 i remember someone telling me of a Hik bullet that had the "right angles" for this, i would guess a longer range one with a 5-50 lens or similar